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Commitments And Contingencies (Environmental) (Details) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Environmental [Roll Forward]    
Beginning balance – January 1 $ 710 $ 758
Reductions for payments made (69) (61)
Changes in estimates 48 65
Ending balance – September 30 $ 689 $ 762